This project will test the hypothesis that diabetic complications are the result of oxidative stress imposed by longterm exposure to aldehydes, specifically glucose and certain metabolites of glucose, and that the extent of this oxidative stress in part is related to the level of the enzyme aldose reductase. Blood cells and plasma from longterm diabetics with or without complications will be compared for evidence of oxidative stress and for levels of aldose reductase as well as other enzymes that may contribute to oxidative stress.